Re: [10/15] Basic value access routines

Doug Evans
2009-06-24T16:26:09Z

On Wed, Jun 24, 2009 at 8:46 AM, Daniel Jacobowitz<drow@false.org> wrote:
> On Wed, Jun 24, 2009 at 09:31:16AM -0600, Tom Tromey wrote:
>> A related idea that occurred to me is that, with Jan's type GC, we
>> could detach types from objfiles and "intern" them (something like
>> bcache-for-types).  This would only be a win if there are many
>> identical types distributed across objfiles, though.
>
> There's plenty of identical types within a single objfile.  Load GDB
> with -readnow, and I find 66 copies of the typedef for "FILE", for
> instance.

As a data point, I compiled gdb with -g -O2 and again with -gdwarf-4 -O2.

-rwxr-x--- 1 dje eng 16321609 Jun 24 08:52 gdb
-rwxr-x--- 1 dje eng 13019406 Jun 24 08:50 gdb-dw4

Starting gdb with -readnow and then examining space usage:

-g -O2:
gdb$ ps l 24343
F UID PID PPID PRI NI VSZ RSS WCHAN STAT TTY TIME COMMAND
0 67641 24343 24342 20 0 117356 97764 - S+ pts/13 0:00 ../../../..

-gdwarf-4 -O2:
gdb$ ps l 24349
F UID PID PPID PRI NI VSZ RSS WCHAN STAT TTY TIME COMMAND
0 67641 24349 16588 20 0 72088 53280 - S+ pts/13 0:00 ../../../..

Until my comdat types patch is vetted more, these numbers are to be
taken with a grain of salt, but they are promising.